JP2008138164A - Active energy beam-curable ink for screen printing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an active energy beam-curable ink for screen printing which is used for screen printing in which screen printing base paper containing at least a film is used as a plate, prevents sticking of the screen printing base paper to a printing part, and is excellent in curability. <P>SOLUTION: The active energy beam-curable ink for screen printing has at least monomer components and a polymerization initiator, wherein the polymerization initiator has an absorbance in terms of the concentration thereof of 100 or less at 365 nm. It is desirable to be used for screen printing in which screen printing base paper containing at least a film is used as a plate. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an active energy ray-curable ink for stencil printing, which is used for stencil printing using a stencil sheet containing at least a film as a plate, and hardly sticks to a printing part of the stencil sheet when left standing.

Conventionally, emulsion ink has been used as stencil printing ink for forming an image with ink that has passed through the perforated portion by using a stencil sheet perforated by heat-sensitive digital plate making. When this emulsion ink is slow to dry and there are many solid portions on the printed matter, it has a problem that the printed matter is set off, that is, when the printed matter that has just been printed is stacked, the ink of the adjacent printed matter adheres and stains the printed matter. is there.
Therefore, instead of the emulsion ink, an active energy ray curable ink has been used. Since the active energy ray curable ink cures rapidly upon irradiation with ultraviolet rays, when printing is performed using the active energy ray curable ink, the ink of the active energy ray curable ink is more than the commonly used W / O emulsion ink. There are advantages such as good drying and not set off.

Various proposals have been made for such an active energy ray-curable ink for stencil printing. For example, in Patent Document 1, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1 (trade name: Irgacure 369, Ciba Specialty Chemicals Co., Ltd.) as a polymerization initiator in Examples. 3 mass%) is used. This polymerization initiator is a polymerization initiator that has absorption up to a long wavelength, has reactivity with light having a wavelength of 365 nm, and has excellent curing characteristics.
However, in Patent Document 1, the stencil sheet on which the image is formed is wound around the outer periphery of the printing part via ink, and when left untreated, the polymerization component oozes out to the non-image part due to capillary force. When exposed to light such as sunlight or a fluorescent lamp, there is a problem that the polymerization initiator works to cure the polymerization component, and the stencil printing base paper is fixed by the printing unit of the printing apparatus, resulting in defective printing.

JP 2002-30238 A

  This invention is made | formed in view of this present condition, and makes it a subject to solve the said problem in the past and to achieve the following objectives. That is, the present invention is used for stencil printing using a stencil sheet containing at least a film as a plate, and prevents the stencil sheet from sticking to a printing part, and has an excellent curing property. The object is to provide ink.

Means for solving the problems are as follows. That is,
<1> An active energy ray-curable stencil for stencil printing, comprising at least a polymerization component and a polymerization initiator, and having a light absorption amount of 365 nm calculated as a concentration of the polymerization initiator of 100 or less. Ink.
The active energy ray-curable ink for stencil printing of <1> has a property that light transmission becomes higher as the film contained in the stencil printing base paper has a longer wavelength, and polymerization in a region with high light transmission is performed. By reducing the light absorption amount of the initiator, specifically, by reducing the light absorption amount of 365 nm converted to the concentration of the polymerization initiator to 100 or less, the action of the polymerization initiator is suppressed, and the polymerization component is cured. It is possible to suppress the reaction and improve defective printing due to fixing of the stencil sheet to the printing part.
<2> The active energy ray-curable ink for stencil printing according to <1>, wherein the light absorption amount at 365 nm is 10 or less.
<3> The active energy ray-curable ink for stencil printing according to <1>, wherein the light absorption amount of any one of 254 nm and 313 nm is 1,600 or more.
<4> The active energy ray-curable ink for stencil printing according to <3>, wherein the light absorption amount at 254 nm is 1,600 or more.
In the active energy ray-curable ink for stencil printing according to any one of <3> to <4>, the light absorption amount of any one of 254 nm and 313 nm is 1,600 or more, particularly, the light absorption amount of 254 nm is 1. , 600 or more, the reaction efficiency of the polymerization initiator is increased, and the effect of promoting the curing reaction of the polymerization component after printing is obtained.
<5> The active energy ray-curable ink for stencil printing according to any one of <1> to <4>, which is used for stencil printing using a stencil sheet including at least a film as a plate.
In the active energy ray-curable ink for stencil printing according to <5>, since the stencil printing base paper includes at least a film, the light transmission becomes higher as the wavelength becomes higher. By reducing the amount of light absorbed by the initiator, the reaction of the polymerization initiator can be suppressed, the reaction of the polymerization component can be suppressed, and the effect of improving defective printing due to fixation of the stencil printing paper to the printing device is improved. To do.
<6> The active energy ray-curable ink for stencil printing according to <5>, wherein the film is a polyethylene terephthalate (PET) film.
In the active energy ray-curable ink for stencil printing according to <6>, since the film is a polyethylene terephthalate (PET) film, the film has an effect of shielding light of 313 nm or less, so that the printing apparatus for stencil printing base paper is used. The effect of improving the defective printing due to the sticking of the toner is further improved.

  According to the present invention, a stencil which can solve the conventional problems, is used for stencil printing using a stencil sheet containing at least a film as a plate, prevents sticking of the stencil sheet to a printing part, and has excellent curing characteristics. An active energy ray-curable ink for printing can be provided.

  The active energy ray-curable ink for stencil printing of the present invention (hereinafter sometimes simply referred to as “ink”) contains at least a polymerization component and a polymerization initiator, and includes a colorant, a dispersant, and a constitution. It contains a pigment, and further contains other components as necessary.

  The ink has a light absorption amount at 365 nm calculated as the concentration of the polymerization initiator of 100 or less, preferably 60 or less, more preferably 10 or less, still more preferably 3 to 10, and most preferably 0. As a result, an effect of improving defective printing due to fixing of the stencil sheet to the printing apparatus can be obtained. As shown in FIG. 1, since the film contained in the stencil printing base paper has a property that the light transmittance becomes higher as the wavelength becomes longer, the light absorption amount of the polymerization initiator in the region having high light transmittance is reduced. This is considered to be because the function of the polymerization initiator can be suppressed and the curing reaction of the polymerization component can be suppressed. In this case, when the film of the stencil printing base paper is a polyethylene terephthalate (PET) film, as shown in FIG. 1, the PET film has a greater characteristic of shielding light of 313 nm or less than the PP film. The effect of improving the defective printing due to the fixing to the printing apparatus is further improved.

  Further, the light absorption amount of either 254 nm or 313 nm in the ink is preferably 1,600 or more, more preferably 2,500 or more, and still more preferably 3,000 to 8,000. The light absorption amount at 254 nm in the ink is preferably 1,600 or more. Thereby, the reaction efficiency of a polymerization initiator is made high and the effect of promoting the hardening reaction of the polymerization component after printing is acquired.

Here, the light absorption amount converted in terms of the concentration of the polymerization initiator was calculated by the following formula 1 from the extinction coefficient of the polymerization initiator in methanol.
<Formula 1>
A = ε · [I]
In the above formula, A represents the absorption amount, ε represents the extinction coefficient (g / g-cm), and [I] represents the concentration of the polymerization initiator in the ink.
Here, the extinction coefficient in methanol of the polymerization initiator was determined by preparing a methanol solution of the polymerization initiator, a quartz cell having a light cell passage length of 1 cm, a spectrometer (manufactured by Soma Optical Co., Ltd., Fastevert S-2400). ) To measure the amount of absorption per cm at each wavelength. The extinction coefficient (g / g-cm) at each wavelength of the polymerization initiator was calculated from the obtained absorption amount and the polymerization initiator concentration. A deuterium / halogen lamp was used as the light source.

As described above, the active energy ray-curable ink for stencil printing of the present invention contains at least a polymerization component and a polymerization initiator, and further includes a colorant, a dispersant, and an extender pigment, and is further necessary. Depending on the, other ingredients are included.
It is preferable that the ink does not contain moisture. In a system containing water, since water absorbs ultraviolet rays, the light absorption amount of the ink converted in terms of the concentration of the polymerization initiator may be different from the case where no water is contained.

Here, the said active energy ray hardening means that a polymerization component superposes | polymerizes and hardens | cures by irradiation of an active energy ray, and this can be confirmed by touching ink after active energy ray irradiation, for example.
Examples of the active energy rays include electron beams and ultraviolet rays.
As the ultraviolet curing light source, commonly used ultraviolet curing lamps such as a high pressure mercury lamp and a metal halide lamp may be used. However, since these lamps have 365 nm light, mercury amalgam lamps are used. It is preferred to use an Eximer lamp.
The ink of the present invention may be composed of a material that is solidified by radical polymerization, or may be composed of a material that is solidified by cationic polymerization.

-Polymerization initiator-
The polymerization initiator is not particularly limited as long as it satisfies the requirement that the light absorption amount at 365 nm calculated by the concentration of the polymerization initiator in the ink is 100 or less, and is appropriately selected according to the purpose. Can do. Examples of the radical polymerization initiator include a photocleavage type and a hydrogen abstraction type, and examples thereof include benzophenone, acetophenone, 4,4′-bisdiethylaminobenzophenone, benzoin, and benzoin ethyl ether. These may be used alone or in combination of two or more.

As the polymerization initiator, a commercially available product can be used. Examples of the commercially available product include IRGACURE series (2959, 651, 127, 184, 907, 369, 379, 819) manufactured by Ciba Specialty Chemicals. DAROCUR series (1173, TPO); Nippon Kayaku Co., Ltd. Kayacure-DETX-S, Kayacure-ITX, benzophenone, acetophenone, 4,4′-bisdiethylaminobenofenone, benzoin, benzoin ethyl ether, etc. .
Among these, IRGACURE 184, 651, 2959, 907; DAROCUR 1173 (both manufactured by Ciba Specialty Chemicals) or Kayacure DETX-S (manufactured by Nippon Kayaku Co., Ltd.) is used in combination with a polymerization accelerator. Particularly preferred.

There is no restriction | limiting in particular as content of the said polymerization initiator, Although it can select suitably according to the objective, 1-25 mass% is preferable with respect to the total mass of the said ink, and 1-10 mass% is more preferable. 3 to 8% by mass is more preferable. If the content is less than 1% by mass, a sufficient effect may not be obtained due to insufficient radicals for polymerization of the polymerization component. If the content exceeds 25% by mass, the polymerization initiator absorbs light. As a result, the amount of light reaching the inside of the ink is reduced, which may cause poor curing inside the coating film.
The polymerization initiator may be used in combination with a sensitizer or a polymerization accelerator. The sensitizer is not particularly limited and may be appropriately selected depending on the intended purpose. For example, n-butylamine, triethylamine , Aliphatic amines such as ethyl p-dimethylamine benzoate or aromatic amines. Specific examples thereof include DAROCUR EDB, DAROCUR EHA (manufactured by Ciba Specialty Chemicals), KAYACURE EPA, and KAYACURE DMBI (manufactured by Nippon Kayaku Co., Ltd.).

-Polymerization component-
The polymerization component is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include a monomer or oligomer modified with urethane-based, epoxy-based, polyester-based, or polyol-based (meth) acrylic acid. Is mentioned.
The oligomer is a low polymer having a degree of polymerization of about 2 to 20 among polymers formed by polymerizing monomers, and means one having one or more acryloyl groups or methacryloyl groups.
The said (meth) acrylic acid means the term which generically refers to acrylic acid, methacrylic acid, and mixtures thereof, and the same applies to other similar expressions.

Examples of the monomer include monofunctional or polyfunctional (meth) acrylate monomers. Examples of the acrylate monomer include dicyclopentyl ethyl acrylate, isobornyl acrylate, phenol ethylene oxide-modified acrylate, tripropylene glycol diacrylate, caprolactone-modified hydroxypivalate ester neopentyl glycol, and 1,6-hexanediol diacrylate. Bisphenol A diglycidyl ether diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate (number of ethylene oxide units 5 to 14), trimethylolpropane triacrylate, pentaerythritol triacrylate, propylene oxide Modified glycerol triacrylate, ethylene oxide ( O) modified trimethylolpropane triacrylate (EO is 1 to 20), propylene oxide (PO) modified trimethylolpropane triacrylate (PO is 1 to 6), pentaerythritol tetraacrylate, ditrimethylolpropane tetraacrylate, pentaerythritol ethoxytetra Acrylate, dipentaerythritol hexaacrylate, 1,4-butanediol dimethacrylate, hexanediol dimethacrylate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, polyethylene glycol dimethacrylate (the number of ethylene oxide units is 5-14), neopentyl glycol dimethacrylate, trimethylolpropa Trimethacrylate, caprolactone-modified dipentaerythritol hexaacrylate, caprolactone-modified trimethylolpropane triacrylate, pentaerythritol tetracaprolactoneate tetraacrylate, ditrimethylolpropane tetracaprolactonate tetraacrylate, ε-caprolactone-modified tris (acryloxyethyl) isocyanurate , Ω-carboxy-polycaprolactone (n = 2) monoacrylate, caprolactone acrylate, and the like.
Examples of the oligomer include epoxy acrylate, epoxy oil acrylate, urethane acrylate, unsaturated polyester, polyester acrylate, and vinyl acrylate.
These may be used individually by 1 type and may use 2 or more types together. Among these, in consideration of safety, it is preferably composed of a material modified with caprolactone, and caprolactone-modified hydroxypivalate ester neopentyl glycol and caprolactone-modified dipentaerythritol hexaacrylate are particularly preferable.

  The viscosity of the polymerization component is preferably 2,000 mPa · s or less, more preferably 800 mPa · s or less, and even more preferably 400 mPa · s or less at 25 ° C. in order to reduce the change in viscosity with respect to temperature. However, from the viewpoint of preventing problems in image quality due to poor fluidity of ink, the viscosity of the polymerization component is preferably 20 mPa · s or more, more preferably 100 mPa · s or more at 25 ° C.

  There is no restriction | limiting in particular as addition amount of the said polymerization component, According to the objective, it can select suitably, 15-95 mass% is preferable with respect to the total mass of the said ink, and 50-85 mass% is more preferable. When the addition amount is less than 15% by mass, the cured film strength may be insufficient, and when it exceeds 95% by mass, a sufficient ink yield value may not be obtained.

-Colorant-
There is no restriction | limiting in particular as said colorant, Insoluble colorants, such as well-known dye of various color tone, a pigment, a disperse dye, can be used according to the objective. In addition, it can also be set as the ink which does not contain a coloring agent for overprinting.
Examples of the colorant include carbon blacks such as acetylene black, channel black, and furnace black; metal powders such as aluminum powder and bronze powder; inorganic pigments such as petals, yellow lead, ultramarine blue, chromium oxide, and titanium oxide; Azo pigments such as insoluble azo pigments, azo lake pigments, and condensed azo pigments; phthalocyanine pigments such as metal-free phthalocyanine pigments and copper phthalocyanine pigments; anthraquinone pigments, quinacridone pigments, isoindolinone pigments, isoindoline pigments, dioxane Gin dyes, selenium dyes, perylene dyes, perinone dyes, thioindigo dyes, quinophthalone dyes, condensed polycyclic pigments such as metal complexes; organic pigments such as lakes of acidic or basic dyes; diazo dyes, anthraquinones Oil-soluble dyes such as dyes; fluorescent pigments That.

The fluorescent pigment is a so-called synthetic resin obtained by dissolving or dyeing a fluorescent dye that develops various hues during or after bulk polymerization of a synthetic resin, and pulverizing and refining the resulting colored bulk resin. Solid solution type resins are preferred, and examples of the synthetic resin carrying a dye include melamine resin, urea resin, sulfonamide resin, alkyd resin, and polyvinyl chloride resin.
Among these, as the carbon black, those having a pH of 6 to 10 may be added, or those having different pH may be used in combination.

  Commercially available products can be used as the colorant. Examples of the commercially available products include MA-100, MA-100S, MA-7, MA-70, MA-77, MA-11, # 40, # 44 (all manufactured by Mitsubishi Chemical Corporation); Raven 1100, Raven 1080, Raven 1255, Raven 760, Raven 410 (all manufactured by Colombian Carbon); Mogul-L, Mulul-E, PEARLS-E (all manufactured by Cabot) ), Etc. These may be used individually by 1 type and may use 2 or more types together.

The colorant is present in a dispersed state in the ink. The average particle size of the colorant dispersed in the ink is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 0.1 to 10 μm, and preferably 0.1 to 1.0 μm. More preferred. If the average particle size is less than 0.1 μm, the pigment may permeate the paper immediately after printing, and the desired effect on the image density may not be obtained. If it exceeds 10 μm, the ink stability is poor. There is.
There is no restriction | limiting in particular as addition amount of the said coloring agent, Although it can select suitably according to the objective, 2-15 mass% is preferable with respect to the total mass of the said ink.

-Extender pigment-
The extender pigment is not particularly limited and may be appropriately selected depending on the intended purpose.For example, white clay, silica, talc, clay, calcium carbonate, organic clay, barium sulfate, titanium oxide, alumina white, diatomaceous earth, Inorganic fine particles such as kaolin, mica, aluminum hydroxide; organic fine particles such as polyacrylate, polyurethane, polyester, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, polystyrene, polysiloxane, phenol resin, epoxy resin; or these Fine particles made of a copolymer of
Further, as the extender pigment, a commercially available product can be used. Examples of the commercially available product include Aerosil series 50, 90G, 130, 200, 300, 380, TT600, COK84, R972, etc. Manufactured by Aerosil Co., Ltd.); white-glazed TDD, white-glazed O (both manufactured by Shiroishi Kogyo Co., Ltd.); TIXOGEL series (VP, DS, GB, VG, EZ-100, MP-100, MP-200, MPI) , MPG, etc.), OPTIGEL (all manufactured by Zude Chemie Catalysts Co., Ltd.); Garamite series 1958, 1210, 2578, Claytone GR, Claytone HT, Claytone PS3 (all manufactured by Southern Clay Products); SG2000 (Nippon Talc Co., Ltd.) Company-made) And so on. These may be used individually by 1 type and may use 2 or more types together.

  There is no restriction | limiting in particular as content of the said extender pigment, Although it can select suitably according to the objective, 0.1-50 mass% is preferable with respect to the total mass of the said ink, and 1-15 mass% is more. 2 to 5% by mass is preferable.

-Dispersant-
The dispersant is a component having a function of dispersing the colorant.
The dispersant is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include sorbitan fatty acid esters such as sorbitan sesquioleate; polyglycerin fatty acid esters such as hexaglycerin polyricinoleate; polyoxyethylene glycerin fatty acid Nonionic surfactants such as esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene alkyl ethers, polyoxyethylene alkylamines, polyoxyethylene fatty acid amides; alkylamine polymer compounds; aluminum chelate compounds; styrene-anhydrous Maleic acid copolymer polymer compound; Polycarboxylic acid ester type polymer compound; Aliphatic polyvalent carboxylic acid; Amine salt of polymer polyester; Ester type anionic surfactant; High molecular weight polycarboxylic acid Long-chain amine salts; salts of long-chain polyaminoamides and polymeric acid polyesters; polyamide-based compounds; phosphate ester-based surfactants; alkyl sulfocarboxylates; sulfonates; α-olefin sulfonates; Examples thereof include salts; polyethyleneimine; alkylolamine salts; resins having dispersibility of insoluble colorants such as alkyd resins. These may be used individually by 1 type and may use 2 or more types together.

  As the dispersant, a commercially available product can be used. Examples of the commercially available product include Solspers series manufactured by Nippon Lubrizol Corporation (for example, S3000, S5000, S9000, S13240, S13940, S16000, S17000, S20000, S24000, S26000, S27000, S28000, S31845, S31850, S32000, S32550, S33000, S34750, S36000, S39000, S41090, S53095, etc.); Plain Act AL-M manufactured by Ajinomoto Fine Techno Co., Ltd. PM821, PB821, PB811, PN411, PA111, etc.); 6220, 6225, 6230, 5244, etc. manufactured by EFKA

  There is no restriction | limiting in particular as addition amount of the said dispersing agent, Although it can select suitably according to the objective, 40 mass% or less is preferable with respect to the total mass of the said coloring agent and extender, and 2-35 mass% is preferable. More preferred.

<Other ingredients>
The other components in the ink of the present invention are not particularly limited and can be appropriately selected according to the purpose within a range not impairing the effects of the present invention. Examples thereof include polymerization inhibitors and vegetable oils. It is done.

-Polymerization inhibitor-
In the ink of the present invention, a polymerization inhibitor may be used for the purpose of storage stability of the ink and prevention of gelation due to a dark reaction.
There is no restriction | limiting in particular as said polymerization inhibitor, According to the objective, it can select suitably, For example, hydroquinone, p-benzoquinone, t-butylhydroquinone, p-methoxyphenol (MEHQ), etc. are mentioned.
The addition amount of the polymerization inhibitor is preferably 100 to 5,000 ppm, more preferably 100 to 500 ppm, based on the total mass of the ink.

-Vegetable oil-
If necessary, the ink of the present invention may use vegetable oil as long as it does not impair the curing properties.
The vegetable oil is not particularly limited and may be appropriately selected depending on the intended purpose.For example, soybean oil, rapeseed oil, corn oil, sesame oil, tall oil, cottonseed oil, sunflower oil, safflower oil, walnut oil, Examples include poppy oil, linseed oil, or vegetable oil obtained by esterifying these. Examples of the ester in the esterified vegetable oil include methyl ester, butyl ester, isopropyl ester, propyl ester, and the like.
These may be used individually by 1 type and may use 2 or more types together. Among these, in consideration of ink drying after printing, it is preferable to use what is generally referred to as drying oil and semi-drying oil having an iodine value of 100 or more. In addition, when the ink fixation on a printing machine by leaving for a long period of time becomes a problem, a vegetable oil having an iodine value of less than 100 may be used.

  When dry oil and semi-dry oil with high iodine value are used as the vegetable oil, it causes an oxidation reaction with oxygen in the air, whereby the oil is dried (solidified), and the ink containing the vegetable oil is also solidified. End up. When the ink is solidified, a problem such as clogging of the screen and deterioration of image start-up occurs. Therefore, when using a vegetable oil having a high iodine value (containing many unsaturated bonds), In order to prevent oxidation of fatty acids (for example, linolenic acid, linoleic acid, oleic acid, etc.), it is preferable to contain an antioxidant described later.

  There is no restriction | limiting in particular as addition amount of the said vegetable oil, Although it can select suitably according to the objective, 5-70 mass% is preferable with respect to the total mass of the said ink, and 30-50 mass% is more preferable.

-Antioxidant-
There is no restriction | limiting in particular as said antioxidant, According to the objective, it can select suitably, For example, amine compounds, such as diphenylphenylenediamine and isopropylphenylphenylenediamine; Phenol compounds, such as tocopherol and dibutylmethylphenol; Sulfur compounds such as mercaptomethylbenzimidazole; dibutylhydroxytoluene, propyl gallate, butylhydroxyanisole, and the like. These may be used individually by 1 type and may use 2 or more types together.

There is no restriction | limiting in particular as addition amount of the said antioxidant, According to the objective, it can select suitably, 2.0 mass% or less is preferable with respect to the said vegetable oil content, 0.1-1.0 mass% Is more preferable.
When the antioxidant is added with a very small amount of antioxidant with respect to the vegetable oil content, an appropriate antioxidant effect may not be expected. On the other hand, a large amount of antioxidant with respect to the vegetable oil content If added at once, it may act as an oxidation accelerator. Therefore, in order to suppress the oxidation of vegetable oil even with a small amount of antioxidant, it is preferable to add a synergist described later.

-Synergist-
The synergist means a compound that itself has little antioxidant action but enhances its action when used in combination with an antioxidant. As the synergist, an acidic substance is usually preferable, and a polyfunctional compound having several hydroxyl groups or carboxyl groups is more preferable.
The synergist is not particularly limited and can be appropriately selected from known ones according to the purpose.For example, methionine, ascorbic acid, threonine, leucine, milk protein hydrolysate, norvaline, ascorbyl palmitate, Phenylalanine, cystine, tryptophan, proline, alanine, glutamic acid, valine, pancreatic protein pepsin digestion solution, asparagine, arginine, barbituric acid, asphenamine, ninhydrin, propanidin, histidine, norleucine, glycerophosphate, casein trypsin hydrolyzate, casein And a hydrochloric acid hydrolyzate. These may be used individually by 1 type and may use 2 or more types together.

  There is no restriction | limiting in particular as an addition amount of the said synergist, According to the objective, it can select suitably, 50-150 mass parts is preferable with respect to 100 mass parts of total mass of the said antioxidant, 70-120 mass parts Is more preferable.

<Method for producing active energy ray-curable ink for stencil printing>
The method for producing the active energy ray-curable ink for stencil printing of the present invention is not particularly limited and may be appropriately selected depending on the intended purpose. For example, each component is mixed by a conventional method and a three-roll mill It can manufacture by performing a dispersion | distribution process using dispersers, such as.
The viscosity of the ink for the stencil printing system is also adjustable by stirring conditions are not particularly limited as long as the viscosity was in the system, can be appropriately selected depending on the purpose, shear rate 20s ^-1 The viscosity is preferably 2 to 40 Pa · s, more preferably 10 to 30 Pa · s.
Further, from the viewpoint of rolling up the paper after printing, the yield value of the ink approximated by the Casson approximation represented by the following formula is preferably 40 to 300 Pa, and more preferably 60 to 200 Pa. The plastic viscosity of the ink is preferably 2.0 Pa · s or less, and more preferably 0.1 Pa · s or more and 1.0 Pa · s or less.

In the above formula, τ represents shear stress. τ ₀ represents a yield value. Eta represents the plastic viscosity. D represents the shear rate.

The active energy ray-curable ink for stencil printing of the present invention is suitably used for stencil printing using a stencil sheet containing at least a film as a plate.
Examples of the stencil printing paper include (1) a film, (2) a film and a Japanese paper, and (3) a three or more layer structure having a porous layer between the film and the Japanese paper. Can be mentioned.
There is no restriction | limiting in particular as said film, Although it can select suitably according to the objective, A thing with low light transmittance is preferable, for example, a polypropylene (PP), a polyethylene terephthalate (PET) etc. are mentioned. Among these, PET has a characteristic of shielding light of 313 nm or less, and is particularly preferable from the viewpoints of cost, punchability, and light transmittance.
Examples of the Japanese paper include those made of natural fibers, those made of synthetic fibers, and those made of natural fibers and synthetic fibers.
Examples of the porous layer include at least one of a porous resin film and a porous fiber film.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

(Examples 1-16 and Comparative Examples 1-2)
-Preparation of UV curable ink for stencil printing-
In accordance with the formulations shown in Tables 1 to 3, a colorant, a dispersant, an extender pigment, a polymerization component (see Table 5), and a polymerization initiator (see Table 4) are mixed, and a three roll mill (manufactured by Inoue Seisakusho Co., Ltd.). The ultraviolet curable ink for stencil printing of Examples 1-16 and Comparative Examples 1-2 was prepared.
About each obtained ink, the light absorption amount in each wavelength was measured as follows. The results are shown in Tables 1 to 3.

<Measurement of light absorption>
The light absorption amount converted in terms of the concentration of the polymerization initiator was calculated by the following formula 1 from the extinction coefficient (see Table 4) of the polymerization initiator in methanol.
<Formula 1>
A = ε · [I]
In the above formula, A represents the absorption amount, ε represents the extinction coefficient (g / g-cm), and [I] represents the concentration of the polymerization initiator in the ink.
Here, the extinction coefficient in methanol of the polymerization initiator was prepared by preparing a methanol solution of the polymerization initiator, a quartz cell having a light cell passage length of 1 cm, a spectrometer (Fastevert S-2400, manufactured by Soma Optical Co., Ltd.). Was used to measure the amount of absorption per cm at each wavelength. The extinction coefficient (g / g-cm) at each wavelength of the polymerization initiator was calculated from the obtained absorption amount and the polymerization initiator concentration. A deuterium / halogen lamp was used as the light source.

The abbreviations in Tables 1 to 3 represent the following contents.
* Mogule-E (Cabot)
* Solsperse 33000 (Nippon Lubrizol Corporation)
* Aerosil 200 (Nippon Aerosil Co., Ltd.)

* All polymerization initiators in Table 4 are manufactured by Ciba Specialty Chemicals.

  Next, for each of the obtained inks, the fixing property of the stencil sheet and the curing property of the ink were evaluated as follows. The results are shown in Table 6, Table 7, and Table 8.

<Fixability test of stencil printing paper>
Apply 0.5 g of ink uniformly to the Japanese paper side of a stencil printing base paper composed of 10 cm square PET film and Japanese paper, adhere to the glass, leave it indoors for one month without shading, and leave the stencil after leaving The state of fixing of the printing base paper to the glass was evaluated according to the following criteria.
〔Evaluation criteria〕
◎: No sticking was observed. ○: Part of the sticking was seen. △: Sticking was observed but could be peeled. ×: Sticking was not possible.

<Printing test (ink curing characteristics)>
About each ink obtained by the Example and the comparative example, it printed with the stencil printing machine (the Ricoh Co., Ltd. make, Satellite A650), and each obtained printed matter was a medium pressure mercury lamp (HOK4 / 120, the Philips company make) of output 400W. ) It was cured using an ultraviolet irradiation device using three. Curing characteristics when the obtained printed matter was rubbed with a cloth were evaluated according to the following criteria.
〔Evaluation criteria〕
(Double-circle): A stain is not seen in both printed matter and cloth.
○: The printed material is not stained, but the fabric is slightly stained.
Δ: Slightly stained but also stained on the printed material.
X: Dirt is seen on the printed matter, and dirt is also seen on the cloth.

  From the results of Tables 1 to 3 and Tables 6 to 8, the inks of Examples 1 to 16 having a light absorption amount of 365 nm converted to the concentration of the polymerization initiator are 100 or less, compared with the inks of Comparative Examples 1 and 2. It can be seen that the stencil sheet can be prevented from sticking to the printing section and has excellent curing characteristics.

  Since the active energy ray-curable ink for stencil printing of the present invention can prevent the stencil sheet from sticking to the printing section and has excellent curing properties, the stencil printing machine uses a stencil sheet containing at least a film as a plate. It is very useful as an ink used in

FIG. 1 is a graph showing transmission characteristics in the ultraviolet region of polypropylene (PP) and polyethylene terephthalate (PET).

Claims (6)

  An active energy ray-curable ink for stencil printing, comprising at least a polymerization component and a polymerization initiator, and having a light absorption amount of 365 nm calculated as a concentration of the polymerization initiator of 100 or less.   The active energy ray-curable ink for stencil printing according to claim 1, wherein the light absorption amount at 365 nm is 10 or less.   The active energy ray-curable ink for stencil printing according to claim 1, wherein the light absorption amount at either 254 nm or 313 nm is 1,600 or more.   The active energy ray-curable ink for stencil printing according to claim 3, wherein the light absorption amount at 254 nm is 1,600 or more.   The active energy ray-curable ink for stencil printing according to any one of claims 1 to 4, which is used for stencil printing using a stencil sheet containing at least a film as a plate.   The active energy ray-curable ink for stencil printing according to claim 5, wherein the film is a polyethylene terephthalate (PET) film.